KA is generally an intermediate relay. KM or K represents a contactor. It is combined with a thermal overload relay to protect the electrical equipment in operation. When the actuating quantity, such as the current or. The relays are in round glass cases. The rectangular devices are test connection blocks, used for testing and isolation of instrument transformer circuits. As per “Reliability Standard PRC-023”, The maximum impedance for the distance relay characteristics along 30o on the impedance plane for 0. They also provide inherent back up with their zones overlapping the protection of the next line, and. The K factor (or zero-sequence compensation factor) adjusts the measured impedance for the phase-to-ground fault loop by accounting for the contribution of zero-sequence currents.
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